The present invention relates to air purifiers and, more particularly, to an air purifier in which a degree of contamination of air is detected to perform adequate operations.
As an air purifier of the kind referred to above, there is one disclosed, for example, in Japanese Patent Laid-Open No. 61-64528. This air purifier is arranged such that light emitted from a light emitting element and scattered by contaminated particles within the air is detected by a light receiving element to determine a degree of contamination of the air. A rotation speed of a blower in an air flow passage provided with a scavenging filter is controlled accordingly. Therefore, a useless or ineffective operation or running of the blower is avoided so as to be capable of reducing the generation of noises and the load of the battery.
On the other hand, in place of removal of the contaminated particles due to the scavenging filter, another arrangement is known (refer to Japanese Patent Laid-Open No. 56-91859), in which the contaminated air flows between electrodes which generate a corona discharge. The contaminated particles in the air are charged and then scavenged effectively or efficiently by downstream scavenging electrodes. In this case, in order to prevent detecting accuracy from being deteriorated by adhesion of the contaminated particles, an electrode for detecting the contaminated particles is additionally provided in place of the above-described light emitting element.
In connection with the above, Japanese Patent Laid-Open Nos. 54-151090 and 56-91859 also disclose such a detecting electrode.
However, for the aforementioned prior art arrangement, since the additional electrode for detecting the degree of contamination of the air is required to be additionally provided, secureness of an establishment location, time of assembling and the like cause new problems. Further, since corona discharge occurs also between the discharge electrode and the detecting electrode, there is a problem that a charge efficiency of the particle is reduced.